In a wind turbine generator, a rotor having blades rotates due to being struck by wind, and a generator coupled to the rotor via a main shaft generates electricity based on the rotation of the rotor. Due to the rotation of the rotor, a load according to the rotation acts on devices such as the main shaft and gear box of the wind turbine generator. For this reason, in order to prevent the load acting on devices such as the main shaft and gear box from exceeding a determined design load in the wind turbine generator, generation of electricity is stopped when speed of wind reaches a predetermined wind speed (cut-out wind speed).
PTL 1 discloses technology for reducing power by lowering the rotational speed of the rotor if the wind striking the wind turbine generator has reached a wind speed that causes wear due to overload.